THIS INVENTION relates to a phosphate ester composition and its use.

The use of phosphate esters of the above general formula (Formula A) as lubricants and flame retardants are well known in the art.
Tri-aryl Phosphate esters (see Formula B below) have been used for many years and are well known in the art as additives for flame retardant plasticizers, flame retardants, anti-wear agents, boundary lubricants, antioxidants as well as functional fluids (self-extinguishing hydraulic fluids).

The first generation tri-aryl phosphates were based on phenol or refined cresols/xylenols from coal tar. These tri-aryl phosphate esters can be ortho [2, 6], meta [3, 5], or para [4] substituted (see Formula C below).

These “natural” materials have been slowly replaced with “synthetic” alkyl phenols (isopropyl, t-butyl, amyl, octyl, nonyl, etc.) as the performance (technical and regulatory) requirements have become more stringent. Unfortunately, in many applications the narrowing of technical performance requirements results in a trade-off with other attributes like regulatory performance and vice versa. Those versed in the art will recognize that for synthetic materials, alkyl substituent(s) is(are) most easily and directly connected at the 2, 4, and 6 positions of the phenol, as per Formula C. Commonly used synthetic alkyl phenols for phosphate esters are mostly substituted at the para (4) position. A drawback of para (mono) substituted synthetic aryl groups is that the resulting tris aryl phosphate ester is a high melt point solid or a high viscosity fluid. This has a deleterious effect on critical properties like liquidity, polymer miscibility, air entrainment, and pour point.
Combinations of triaryl, alkyl-diaryl, and di-alkyl-monoaryl phosphate esters have also been developed to meet specific requirements.
Performance requirements like volatility, exudation, toxicity (acute and neuro-) hydrolytic/oxidative/thermal stability and hazard classification are important properties of phosphate esters when used as flame retardants and lubricants. It is therefore a desire to improve the properties like volatility, exudation, neurotoxicity, without sacrificing pour point, viscosity or fluid life (hydrolytic, thermal, and oxidative stability).
US2003/0078325, incorporated herein by reference for all purposes, teaches the use of triaryl phosphate esters as flame retardants. The aryl ring has a single hydrocarbyl substituent on any carbon atom of the ring structure, with the total carbon number of the substituents being from 3 to 11. The phosphate esters are incorporated into polymer compositions alone or in combination with other flame retardants.
WO2010/149690, incorporated herein by reference for all purposes, discloses the use of triaryl phosphate esters as anti-wear agents with reduced neurotoxicity. Some or all of the aryl groups are mono-substituted with the same alkyl group, which may be located at the ortho-, meta-, or para-position of the ring structure.